In the field of high pressure gas cylinders, it is well-known to fit valves onto such cylinders in order to provide a closable opening to the cylinder. Such cylinders tend to contain gases such as natural gas or hydrogen, and can also be used to contain other gases such as nitrogen, helium, argon or air. The valve can be opened to allow either the filling or emptying of the gas cylinder, and then can be closed again once this operation is complete.
A disadvantage with these valves, which are generally made of brass or steel, is the inefficiency of the flow of the gas through the valve. One way of quantifying the efficiency of a particular valve is to calculate its net discharge coefficient. This is calculated as follows (by reference to know prior art valves). For example, the OMB™ Beta New valve has a 7 mm orifice (i.e., the cross-section of the narrowest part of the conduit through the valve) with a filling flow equal to a 5.194 mm ideal orifice. The net CD is calculated as (5.194)2/(7)2=55%. Similarly, the VTI™ valve V-VTK905 has a 5.8 mm orifice with filling flow equal to a 4.42 mm ideal orifice. Thus, the net CD is (4.42)2/(5.8)2=58%.
There is therefore a need in the art to provide valves with improved flow characteristics, while also meeting the high safety standards required of such high pressure gas cylinder valves. It is also desirable to seek to improve the seals provided in such valves, for example to improve the lifetime and performance of the seals.